My Russian is a very long way from perfect but key extracts as I understand them...

- 2 jumpers with 900 and 200 jumps were jumping from an AN2 at about 4,500 feet

- jumpers were aged 53 and 43

- 8 January is part of the long Christmas holidays in Russia

- they decided they wanted to get extended free fall time so switched off their AADs before the jump

- witnesses on the ground suggested the men started to deploy their mains at about 100m. both impacted with no mains (seems like perhaps one of the pilot chutes inflated but nothing else)

- minus 25c at ground level on the day of the jump

I don't know the DZ, the area or the jumpers. My guess would be that if this was their main dz, they would be used to jumps from a similar altitude and may not have had an awareness of how much free fall time would be "safe" from 4,500 feet. At this time of the year, the ground would most likely be covered by deep snow. whether this impacted their ability to "eyeball" the ground is not stated but could be a possibility. I have no idea whether they would be using altis.

If not used to freefall in such temperatures, it is possible that their goggles (which could be fine for delays of a few seconds) may not have been adequate for longer periods of freefall (adequate in terms of enabling them to see clearly).